Polycarbonate has found many uses because, in general, it combines a high level of heat resistance and dimensional stability with good insulating and noncorrosive properties, and it is easily molded. However, its ductility is often reduced by contact with organic solvents such as gasoline. In blends of polycarbonate with other polymers such as polyester, especially in those blends also containing an impact modifier, a balance of properties is consequently sought for the purpose of arriving at a useful level of both impact and solvent resistance.
References are known which disclose compositions of polycarbonate, polyester, an epoxide-containing modifier and a grafted impact modifying copolymer. Among these are Chung, U.S. Pat. No. 4,554,315, Lausberg, U.S. Pat. No. 4,912,163, EP 386,674-A and JP 62-184,051-A (1987). However, no recognition exists in any of these references of the possibility of strengthening polycarbonate while maintaining a useful level of solvent resistance, low gloss and good flexural modulus and weldline strength by employing in place of the grafted copolymer a thermoplastic elastomer, or a rubber-modified sytrene/acrylonitrile copolymer, particularly that which is mass produced.
It has been found, however, that the use of a thermoplastic elastomer or a rubber-modified sytrene/acrylonitrile copolymer in a blend of polycarbonate, polyester and an epoxy-containing modifier does result in a composition which, when molded, possesses a good balance of processing and physical properties, for example a desirably high level of solvent and impact resistance, as well as low gloss.